PDBsum entry 2ab9

Hydrolase inhibitor

PDB id: 2ab9

Contents

Protein chain

31 a.a.

PDB id:

2ab9

Name:

Hydrolase inhibitor

Title:

Discovery, structural determination and processing of the precursor protein that produces the cyclic trypsin inhibitor sfti-1

Structure:

Pro-sfti-1. Chain: a. Engineered: yes

Source:

Helianthus annuus. Common sunflower. Organism_taxid: 4232. Expressed in: escherichia coli. Expression_system_taxid: 562.

NMR struc:

20 models

Authors:

J.P.Mulvenna,F.M.Foley,D.J.Craik

Key ref:

J.P.Mulvenna et al. (2005). Discovery, structural determination, and putative processing of the precursor protein that produces the cyclic trypsin inhibitor sunflower trypsin inhibitor 1. J Biol Chem, 280, 32245-32253. PubMed id: 16036912 DOI: 10.1074/jbc.M506060200

Date:

15-Jul-05 Release date: 26-Jul-05

Protein chain

Q4GWU5  (SFTI1_HELAN) -  Trypsin inhibitor 1 from Helianthus annuus

Seq: 56 a.a.

Struc: 31 a.a.

DOI no: 10.1074/jbc.M506060200

J Biol Chem 280:32245-32253 (2005)

PubMed id: 16036912

Discovery, structural determination, and putative processing of the precursor protein that produces the cyclic trypsin inhibitor sunflower trypsin inhibitor 1.

J.P.Mulvenna, F.M.Foley, D.J.Craik.

ABSTRACT

Backbone-cyclized proteins are becoming increasingly well known, although the mechanism by which they are processed from linear precursors is poorly understood. In this report the sequence and structure of the linear precursor of a cyclic trypsin inhibitor, sunflower trypsin inhibitor 1 (SFTI-1) from sunflower seeds, is described. The structure indicates that the major elements of the reactive site loop of SFTI-1 are present before processing. This may have importance for a protease-mediated cyclizing reaction as the rigidity of SFTI-1 may drive the equilibrium of the reaction catalyzed by proteolytic enzymes toward the formation of a peptide bond rather than the normal cleavage reaction. The occurrence of residues in the SFTI-1 precursor susceptible to cleavage by asparaginyl proteases strengthens theories that involve this enzyme in the processing of SFTI-1 and further implicates it in the processing of another family of plant cyclic proteins, the cyclotides. The precursor reported here also indicates that despite strong active site sequence homology, SFTI-1 has no other similarities with the Bowman-Birk trypsin inhibitors, presenting interesting evolutionary questions.

Selected figure(s)

Figure 1.
FIGURE 1. A ribbon depiction of the structure of a BBI from Glycine max (soybean, PDB code 1BBI [PDB] ) with the chymotrypsin and trypsin-reactive loops highlighted is shown. The detailed structure of the trypsin inhibitory loop is shown below the ribbon diagram and alongside the solution structure of SFTI-1 (PDB code 1JBL [PDB] ). In both cases the Cys residues and the lysine residue in the P1 position (45) are highlighted with the side chains depicted in stick form. The inset shows SFTI-1 (PDB code 1JBL [PDB] ) superimposed with the reactive loops of BBIs from mung bean (PDB code 1SMF [PDB] ), adzuki bean (PDB code 1TAB [PDB] ), and soybean (PDB code 1BBI [PDB] ). For orientation purposes, the Cys residues have been labeled on SFTI-1.

Figure 6.
FIGURE 6. Superimposition of the reactive site loops of pro-SFTI-1 (PDB ID 2AB9 [PDB] ), cyclic SFTI-1 (PDB ID 1JBL [PDB] ), and the trypsin inhibitory loop of the soybean BBI (PDB ID 1BBI [PDB] ). Cys residues are highlighted, and the Cys numbering of pro-SFTI-1 is indicated for reference.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2005, 280, 32245-32253) copyright 2005.

Figures were selected by an automated process.